Lampholder



Feb. 25, 1964 w. vERMEuLl-:N 3,122,404

LAMPHOLDER Filed Dec. 31, 1962 2 Sheets-Sheet 1 -f-*ZS 2 2 H um? #44444/Il A' INVEN TOR.

W/Z//m Verwey/ff?, BY Jmd.; 62..

Attorney Feb. 25, 1964 w. VERMEULEN LAMPHOLDER 2 Sheets-Sheet 2 FiledDec. 31, 1962 United States Patent O M' 3,122,434 LAMPHGLDER WilliamVermeuien, Fairfield, Sonn., assigner to Ge erai Elecnic Company, acorporation of New York Filed Dec. 31, 1962, Ser. No. 248,413 7 Claims.(fCl. 339-52) The present invention relates to lampholders fordoubleended electric discharge lamps, such as iluorescent lamps, and inparticular to fluorescent lampholders employing a movable plunger typeof contact positioning member.

Prior art fluorescent lamps have commonly been supported and suitablyenergized by means of a pair of lampholders, one of which includes aretractable or compressible plunger for positioning the contactsthereof. Such a lampholder is commonly referred to as a compressiblelampholder. To enable the contact elements of these prior artcompressible lampholders to efciently interengage their mating contactsin associated uorescent lamps, it has been considered both important anddesirable for the lampholder contact elements to eXert a biasing forceupon the seated lamp contacts in a direction transverse to the axis ofmovement of the plunger. Such a transverse biasing force imparted by thelampholder contact element to its associated lamp contact, assures aneffective wiping action between the contacts.

In the past it has been a widespread practice to construct compressiblelampholders of the nature referred to, with one or more springs forbiasing separate and distinct contact elements and the plunger itselfinto the desired positions in the lampholder. The costs of these priorart lampholders have reilected a considerable expense due to labor andmaterial costs which result from the use of the several parts and theshop operations required in assembling the lampholder. It has,therefore, been found desirable to provide an improved iluorescentlampholder which is simple in construction, relatively easy to assemble,and of substantially reduced overall cost, while at the same timeproviding an effective contact wiping action.

Accordingly, it is a primary object of my invention to provide animproved fluorescent lampholder which is very eiiicient in operation anddue to its relative simplicity can be manufactured at a reduced cost.

Another object of my invention is to provide an improved iuorescentlampholder wherein a compressible contact positioning plunger isutilized, and novel contact elements are included which bias the plungerinto its operating position and also effect an efficient contact wipingaction upon interengagement with cooperating lamp contacts.

A further object of my invention is to provide an improved uorescentlampholder which is compact and very reliable in operation.

In carrying out my invention, in one form thereof, l have provided alampholder for receiving the contacts of a double contact uorescentlamp. The lampholder includes an insulating housing, and a Contactpositioning plunger arranged in the housing for reciprocating movementrelative thereto. The plunger has a transverse wall recessed from itsouter end to provide an outwardly facing cavity for receiving a lampbase. A central projection is formed within this cavity. This centralprojection has a pair of grooves formed on its opposite sides. In myimproved arrangement, a pair of contact making springs are arranged inspaced apart and insulated relationship within the lampholder housing.Each of these springs includes a first resilient section disposed at oneof its ends and a second resilient section comprising the remainderthereof. The first resilient Sections of the springs are extendedthrough openings formed in the BZZAM Patented Feb. 25, 1964 ICCtransverse wall so that they terminate within the outwardly facingcavity. The second resilient sections are arranged in compressionbetween the housing and inner surfaces of the plunger to position thefir-st spring sections outwardly from the transverse wall. The firstspring sections `of the springs each include a contacting iinger and ameans for pivoting this contacting linger into wiping engagement with alamp contact. With this arrangement, when the base of a lamp is seatedinto interengagement with the lampholder, the pivoting means, whichincludes the first spring sections, causes the contacting finger toexert a laterally directed contact pressure upon mating contacts of thelamp. This laterally directed Contact pressure is in a directiontransverse to the axis of movement of the plunger and it provides anexcellent electrical contact wiping action while at the same timetending to mechanically retain the lamp base in secure interengagementwith the lampholder.

Further aspects of my invention will become apparent hereinafter, andthe speciication concludes with claims particularly pointing out anddistinctly claiming the subject matter which l regard as my invention.The invention, as to organization and method of operation, together withfurther objects and advantages thereof, may best be understood byreference to the following description, when taken in coniunction withthe accompanying drawings, in which:

FIG. l1 is a side elevational view of a compressible lampholderembodying one form of my invention, and one end of a fluorescent lamp inengagement with the lampholder;

FIG. 2 is a sectional view of the lampholder of FIG. l, taken generallyalong the line 2 2 of FIG. 1;

FIG. 3 is an enlarged fragmentary sectional view of yone side of thecontact positioning member of the lampholder of FIG. I1, showing thearrangement of the contacting spring therein;

FIG. 4 is a view similar to FlG. 2, with part of the contact positioningmember shown in full, and the base end of the fluorescent lampinterengaging the lampholder;

FIG. 5 is an enlarged fragmentary sectional view of a second form ofcontacting spring embodying my invention;

PIG. 6 is a View similar to FIG. 5, showing a first lamp base contactinterengaged with the contacting spring; and

FIG. 7 is a view similar to FIG. 6, showing a second form of lamp basecontact interengaged with the contacting spring.

Referring to FG. l of the drawings, in which like numbers denote likeparts in all the figures, there is illustrated one end of a conventionaltype of double-ended uorescent lamp l which interengages a compressiblelampholder 3 constructed in accordance with my invention. The lampholderf3 is suitably secured to a support (not shown) of a lighting fixture.The other and opposite end (not shown) of the lamp i interengages astationary lampholder (not shown) and the lamp 1 is thus removablyarranged in compression between the stationary lampholder and thelampholder 3, in the Well known manner.

As shown in FIGS. l and 4, the lamp 1 has a tubular glass envelope 5provided with a base 7 located at the end of the lamp 1 which engagesthe lampholder 3. The lamp base 7 comprises an annular metal shell 9 andan insulating element 11 secured thereto. The element 11 includes anannular flanged portion 12 which is secured to the shell 9, and an ovalshaped embossment 13, part of which is shown in section in FIG. 4. Theembossment i3 has a passageway 15 formed therein, and on opposite sidesof passageway l5 a pair of lamp contacts 17 are secured to theinsulating element li, one of these lamp contacts l? being shown in FIG.4. rEhe lamp contacts 17 thus extend inwardly through passageway l5 intothe glass envelope 5, for connection to a suitable electrode (notshown). The outer ends of the lamp contacts 17 are bent over and awayfrom the longitudinal axis of the envelope 5, and then doubled back, asshown in FIG. 4, to form a substantially U-shaped termination. TheU-shaped termination of each Contact i7, thus includes an inner surface19 parallel to the of tl e envelope, an outwardly facing transversesurface 2l perpendicular to the axis of the envelope, and ent. section23 which is doubled back parallel to surface lil. As shall be furtherexplained hereinafter, the surfaces i9 and 2li are electrically andmechanically interengageable with cooperating contacts of the lamrholder3. The end section 23 of the lamp Contact i7 cooperates with tembossment 13 to help clamp the contact i7 in its position on the outerface of the lamp base. As further shown in FIG. 4, the U-shapedterminations of the lamp contacts 17 are recessed inwar ly from theutermost face 13a of embossment i3 of the lamp base.

Turning now to an important aspect of the present invention, whichconcerns an improved compressible lampholder 3 which is efcient inoperation and economical in cost, attention is directed to FIG. 2. Thecompressible lampholder 3 comprises a housing 25 of suitable insulatingmaterial elfected by the securement of front and back base members 27and 29 in cooperative relationship. The front base member 27 faces tothe left (viewing FIGS. l and 2) and it includes a recessed charnber 3lopening into outer end 33 thereof. Within the chamber 3l there isreciprocably and telescopically arranged a contact positioning plunger35 which combines with the housing members 27 and 29 to form aninsulative housing for a pair of Contact making springs 37 of thelampholder. The structure and arrangement of the springs 37 comprises animportant part of my invention, as shall be further understoodhereinafter.

For telescopically receiving plunger 35, the chamber 3l includes agenerally cylindrical cavity 39 and a pair of diametrically opposedgrooves formed in the inner walls thereof. The plunger 35 has agenerally cylindrical external configuration of less diameter than thecylindrical cavity 39 and is provided with diametrically opposed ears ilwhich project radially outwardly from the plunger 35 and fit into theaforementioned grooves to guide the reciprocating movement of theplunger in cavity 39.

As shown in FIGS 2 and 4, the contact making springs 37 are arranged inspaced apart relationship within the overall housing provided by theplunger 35 and housing members 27 and 29. Each of the springs 37 is ofelongated construction and includes an elongated helical scction 43which forms a substantial portion of the spring and extends from theright end 45 (viewing FIG. 2) toward the left end 47 (FIG. 2). On andnear the left end 47 of the springs 37, as best shown in FIG. 3, thereis formed an irregularly looped contact making and wiping section 49.

To preclude any undesirable lateral movement of spring end d5, thehelical section 43 has its outer end i5 fitted around suitable terminalmembers l, which are supported in the back housing member 2%. Thus, moreparticularly as shown in FIGS. 2 and 4, the inner surtace of back member29 facing plunger 35, has the terminal members 51 mounted thereon. Eachof the two terminal members 5l includes an annular boss 53 which isreceived by the outermost end 45 of the helical section 43 of spring 37to accurately position the one end of the spring 37 in chamber 3l of thelampholder 3. The other and inner ends 55 of the helical sections t3 ofthe springs 37 are arranged in cylindrical recesses 57 formed on theinner end of plunger 35. Ends 55 are seated longitudinally against andengage annular shoulders 5@ of their associated plunger recesses 57.Thus, as shown in FIGS. 2

d. and 4, the helical sections 43 of the contact making springs 37 arearranged in continuous compression between annular shoulders 59 of theirassociated plunger recesses 57 and the inner surface of housing member29 to continuously bias the contact positioning plunger 35 to itsoutermost position (as shown in FIG. 2).

Turning now to the structure of the contact making and wiping section i9of each of the contact making springs 37, attention is directed inparticular to FIG. 3. As shown therein, the inner end 55 of helicalsection 43 of each spring 37 is bent over at 6l and connected to anintegral supporting leg 63. The leg e3 extends in a direction parallelto the axis of movement of plunger 35. In addition, leg 63 is alsopreferably disposed in a plane which includes the longitudinal axis ofhelical section 43, and it is connected by a bend 65 to a generallyL-shaped contacting portion 67 which is also in the same plane. TheL-shaped contacting portion 67 includes a generally transverse branch(i9 which is disposed in generally perpendicular relationship to theaxis of movement of plunger 35. rThe branch 69 is connected by bend 7lto limb 73 to form the remainder of the L-shaped contacting portion 67.The limb 73 is preferably constructed and arranged in the plunger 35 sothat it is parallel t0 the axis of movement of the plunger.

As shown in FIG. 3, the limb 73 of the L-shaped connecting portion 67forms one side of a doubled back or looped over outermost end 75 of thecontact making and wiping section 49. The other side of the doubled backend 75 includes inner end portion 77. End portion 77 is disposed ingenerally parallel relationship to limb 73, and is normally contiguousto surface 78 of the central insulating projection Sil, which separatesthe contact sections 49.

As shown in FIG. 3, it will also be noted that free end Sl of the endportion 77 of the contact section 49 engages a transverse step 33 of aplunger shoulder 35. The sdoulder S5 is formed on the inner side of aplunger slot 89 through which the contact making and operating section49 is extended (FIG. 3). In accordance with the present invention, thelocation of the free end 81 of end portion 77 in engagement with step 33of the plunger enables the contact making and operating section e@ topivot laterally to the dotted position shown in FIG. 3, upon engagementof lamp contact 17 with transverse branch 69 of section e9. This mode ofoperation shall now be set forth in detail.

As shown in FIG. 2, when the lamp base 7 of lamp 1 is disengaged from mycompressible lampholder 3, the helical sections 43 of the two springs 37are arranged in compression between back housing member 29 and annularshoulders 59 (FIG. 3) of the plunger recesses 57, to resiliently biasthe contact positioning plunger 35 to its outermost position. When theplunger 35 is in this position, the looped over outermost ends 75 of thecontact making and wiping sections i9 are positioned as shown in FIG. 2,and in solid lines of FIG. 3, with end portion 77 contiguous toinsulating surface 78 of the plunger, and end 81 of the Contact section49 engaging plunger step 83.

When the lamp base 7 of lamp l is then inserted into interengageme-ntwith the open mouth of the compressible lampholder 3, as the transversesurfaces 2l of the lamp contacts 17 engage transverse branches 69 (FIG.3) of the springs 37, the contact making and wiping section 49 pivotsabout step S3 to the dotted position shown in FIG. 3. As a result of thepivoting action which is chieved by the Contact wiping section 49, thelooped over outermost end 75 of each of the springs moves laterally awayfrom the central insulating projection of the plunger. The surface oflimb 73 which is closest to the inner surface il? of the lamp contact 17thereupon impinges against and exerts a laterally directed biasing forceupon inner surface 19' of the lamp.

It will thus be seen that the engagement of transverse surfaces 2l ofthe lamp contacts i7 with transverse branches 69 (IFlG. 3) of thecontact mal ing and wiping sections 49 causes an eicient pivotingmovement of the contact Vsection 49 to effect a lateral wiping action ofthe limbs 73 into secure electrical engagement with the lamp contacts17. Such an arrangement provides an excellent electrical connectionbetween the lampholder contact springs 37 and the lamp contacts 17. Itwill further be understood that the springs 37 not only provide thecontact wiping sections 49 for effective engagement with the lampcontacts .17, but they also include an integral means in the form ofhelical sections 43 for biasing the plunger 35 to `its outermostposition. The contact making springs 37 may by way of example beconstructed of Phosphor bronze spring wire having a diameter in theorder of 0.036 inch.

FIGS. 5, 6 and 7 represent a modified form of my invention whereincontact making springs 137 have been empiloyed in the plunger 35. Spring137 differs from spring 37 with respect to the configura-tion of thecontact making and wiping section 149 (FiG. 5). For spring 137 and i-tsillustrated lamp Contact 117, the component parts and sections thereofshown in MGS. -7 which have a structural similarity to their correlativeparts of spring 37 and lamp contact 17, respectively, are identiiied bythe same two reference numerals, with the numeral =1 prefixed thereto.

As shown yclearly in FlG. 5, the con-tact operating and wiping section149 of spring 13-7 has, in general, a double-L or W shapedconfiguration. :In particular, section 149 includes supporting leg 163,which is bent upwardly at 161 from inner end 155 of helical section 143.Leg 163 extends in a direction generally parallel to the axis ofmovement of plunger 35. yIn addition, leg 163, as well as all of thecontact section 149, is preferably disposed in a plane which includesthe longitudinal axis of helical section 143, and it is connected bybend '165 to a generally L-shaped contacting portion 167. The L- shapedcontacting portion 167 includes a transverse branch 169 which isdisposed in generally perpendicular relationship to the axis of movementof plunger 35. The branch 169 is connected by bend 171 to limb 173 toform the remainder of the L-shaped contacting portion 167. The limb 173lis normally disposed parallel to supporting leg 163, and it isconnected at bend 174 to ou-ter transverse section 190. .The section 190is normally disposed in outwardly yspaced relationship from step 192 ofplunger 35 (as shown in fFIG. 5) when the lamp 5 is disengaged from thelampholder.

With the contact spring 137 in the position shown in FIG. 5, when thelamp contact i117 of a fluorescent lamp base is inserted intointerengagement with the open mouth of plunger 35, the inner surface 119of the lamp contact may first impinge upon the curved upper end of limb173, or upon the curvature of bend 174. When this interengagementcondition occurs, the impingement of inner surface 119 of the lampContact 117 causes the Contact section to move to the position where itis shown in FIG. 6. Transverse seion .190 then engages step 192 of theplunger. Limb 173 then exerts a compressive force upon inner surface 119of the lamp contact, which force is directed laterally and to the right,viewing FIG. 6. This compressive biasing force provides an effectivelateral wiping action of contact section 149 into secure electricalengagement with lamp contact 117 (FIG. 6).

It is now supposed that the lamp contact -117 is arranged so that whenit is thrust downwardly linto engagement with spring 137, transversesection 121 of the lamp con-tact rst engages transverse branch 169 ofthe lampholder contact section y149 before inner surface 119 of the lampcontact performs any positive engaging function. The result of such -acondition is illustrated in FIG. 7. Thus, when transverse section 121 ofthe lamp contact engages branch 169 of the lampholder contact first, theouter section 196 pivots about edge 192er of the step 192. This causesthe bend or elbow 174 (FIG. 5) to impinge upon inner surface 119 of thelamp contact to exert a compressive biasing force thereupon, which isdirected laterally and to the right, viewing iFIG. 7. This compressivebiasing force provides `an effective lateral wiping action of contactsection 149 into secure electrical engagement with lamp contact 117(IFIG. 7).

It will now, therefore, be seen that the present invention provides anovel and improved fluorescent lampholder which is etiicient inoperation, and which due to its relative simplicity may be economicallymanufactured. It will further be understood that the improved contactspring arrangements of the present invention perform Ia plurality ofeliicient functions in an expeditious manner.

While in vaccordance with the patent statutes, I have described what atpresent are considered to be the preferred embodiments of my invention,it will be obvious to those skilled in the art that various changes andmodifications may be made therein without departing from my invention,and I, therefore, aim in the following claims to cover all suchequivalent variations as fall within the true spirit and scope of thisinvention.

What I claim as new and desire to secure by Letters Patent of the UnitedyStates is:

l. A fluorescent lampholder comprising an open ended casing, a contactpositioning plunger arranged for reciprocation in said casing andsubstantially closing the open end thereof to form a housing for thelampholder, said contact positioning plunger having an outer faceadapted to receive a vlamp base, a centrally disposed insulative spacingmeans within said plunger, and a pair of spaced apart Contact wipingsprings located in said housing `and separated by said spacing means,each of said springs including a lirst resilient section disposed at oneof its ends and a second resilient section comprissing the remainderthereof, said first resilient sections being exposed at said outer faceof said plunger for engaging contacts of said lamp base, said secondresilient sections being arranged in compression between said casing andsaid plunger thereby to bias said contact positioning plunger outwardlyfrom said casing and to bias said first spring sections in the samedirection as said plunger, said iirst resilient sections engaging saidspacing means and being held thereby against axial movement into saidplunger and pivoting thereon to exert a laterally directed contactpressure upon the contacts of said lamp when said lamp is seated in saidlampholder.

2. A fluorescent lampholder comprising yan open ended casing, a contactpositioning plunger arranged for reciprocation in said casing andsubstantially closing the open end thereof to form a housing for thelampholder, said contact positioning plunger having an outer faceadapted to receive a lamp base, a centrally disposed wall within saidplunger, a pair of spaced apart contact wiping springs located in saidhousing and separated by said wall, each of said springs including afirst resilient section disposed at one of its ends and a secondresilient section comprising the remainder thereof, said first resilientsections being exposed at said outer face of said plunger -for engagingcontacts of said lamp base, said second resilient sections having ahelical configuration and being arranged in compression between saidcasing and said plunger thereby to bias said contact positioning plungeroutwardly from said casing and to bias said first spring sections in thesame direction as said plunger, said plunger including steps locatedrespectively in contiquity with each yof said first resilient sections,and said first resilient sections each including a leg engaging anassociated step and pivoting thereon when the contacts of said lamp areseated in said lampholder, causing said rst resilient sections to exerta laterally directed contact pressure upon the contacts of said lamp.

3. The fluorescent lampholder of claim 2 wherein the first resilientsections each include a substantially L- shaped contact engagingsection.

4. The fiuorescent lampholder of Claim 2 wherein the yiirst resilientsections of the contact wiping springs each include a substantiallyL-shaped Contact engaging section, a first leg of said L-shaped contactengaging section being disposed in transverse relationship to thelongitudinal axis of said second resilient sections, a second leg ofsaid 'contact engaging section being disiosed generally parallel to thelongitudinal axis of said second resilient sections, and an end portionof said first resilient section doubled back into parallel relationshipwith said second leg and extending inwardly toward said second resilientsection, the free end of said end portion of said first resilientsection of each of said springs being arranged in engagement with anassociated step on said central wall lthereby to pivot said firstresilient sections laterally upon interengagement of said Contact wipingsprings with associated contacts of said lamp.

5. The liuorescent lampholder of claim 2 wherein the first resilientsections of `the contact wiping springs each include a substantiallyL-shaped contact engaging section, a iirst leg of said L-shaped contactengaging section being disposed in transverse relationship to thelongitudinal axis of said second resilient section, a second leg of saidcontact engaging section being disposed generally parallel to thelongitudinal axis of said second resilient section, and an end portionof said first resilient section disposed in transverse relationship tothe longitudinal axis of said second resilient section, said end portionbeing disposed in proximity to an associated step on the inner Wall ofsaid plunger and arranfred to pivot upon an edge of said step when thecontacts of said lamp are seated in said lampholder, thereby to exert alaterally directed Contact pressure upon an associated lanp contact.

6. A fluorescent lampholder comprising an open ended casing, a contactpositioning plunger arranged for reciprocation in said casing andsubstantially closing the open end thereof to form a housing for thelampholder, said contact positioning plunger having an outer `faceadapted to receive a lamp base, and wall means within said plunger, atleast one contact wiping spring located in said housing, said springincluding a first resilient section disposed at one of its ends and asecond resilient section comprising the remainder thereof, said firstresilient section being exposed at said outer face of said plunger forengaging a contact of said lamp base, said second resilient sectionbeing arranged in compression between said casing and said plungerthereby to bias Said Contact positioning plunger outwardly from saidcasing and to bias said first spring section in the same direction assaid plunger, said first resilient section engaging said wall means andbeing held thereby against axial movement into said plunger and pivotingthereon to exert a laterally directed contact pressure upon the contactof said lamp when said lamp is seated in said lampholder.

7. A liuorescent lampholder comprising an open ended casing, a contactpositioning plunger arranged for reciprocation in said casing andsubstantially closing the open end thereof to form a housing for thelampholder, saidV contact positioning plunger having an outer faceadapted to receive a lamp base, a pair of spaced apart contact wipingsprings located in said housing, each of said springs including a firstresilient section disposed at one of its ends and a second resilientsection comprising the remainder thereof, said first resilient sectionsbeing exposed at said outer face of said plunger for engaging contactsof said lamp base, said second resilient sections having a helicalconfiguration and being arranged inl compression between said casing andsaid plunger thereby to bias said contact positioning plunger outwardlyfrom said casing and to bias said first spring sections in the samedirection as said plunger, a centrally disposed insulating wall withinsaid plunger near the outer face thereof, said wall being disposedbetween the first resilient sections of said springs and including astep located in contiguity with each of said first resilient sections,said first resilient sections each including a leg engaging and pivotingon an associated step when the contacts of said lamp are seated in saidlampholder, thereby to exert a laterally directed contact pressure uponthe contacts of said lamp, said step being recessed and disposed in theouter face of said plunger and engageable with said leg Y of said firstresilient section, thereby to accurately position said first resilientsection in the outer face of said plunger and preclude any undesirabledislodgment therefrom.

References Cited in the file of this patent UNITED STATES PATENTS2,716,738 Pistey Aug. 30, 1955 2,722,666 Hodgkins Nov. 1, 1955 2,977,563Lennox Mar. 28, 1961 FOREIGN PATENTS 795,439 Great Britain May 21, 1958r

6. A FLUORESCENT LAMPHOLDER COMPRISING AN OPEN ENDED CASING, A CONTACTPOSITIONING PLUNGER ARRANGED FOR RECIPROCATION IN SAID CASING ANDSUBSTANTIALLY CLOSING THE OPEN END THEREOF TO FORM A HOUSING FOR THELAMPHOLDER, SAID CONTACT POSITIONING PLUNGER HAVING AN OUTER FACEADAPTED TO RECEIVE A LAMP BASE, AND WALL MEANS WITHIN SAID PLUNGER, ATLEAST ONE CONTACT WIPING SPRING LOCATED IN SAID HOUSING, SAID SPRINGINCLUDING A FIRST RESILIENT SECTION DISPOSED AT ONE OF ITS ENDS AND ASECOND RESILIENT SECTION COMPRISING THE REMAINDER THEREOF, SAID FIRSTRESILIENT SECTION BEING EXPOSED AT SAID OUTER FACE OF SAID PLUNGER FORENGAGING A CONTACT OF SAID LAMP BASE, SAID SECOND RESILIENT SECTIONBEING ARRANGED IN COMPRESSION BETWEEN SAID CASING AND SAID PLUNGERTHEREBY TO BIAS SAID CONTACT POSITIONING PLUNGER OUTWARDLY FROM SAIDCASING AND TO BIAS SAID FIRST SPRING SECTION IN THE SAME DIRECTION ASSAID PLUNGER, SAID FIRST RESILIENT SECTION ENGAGING SAID WALL MEANS ANDBEING HELD THEREBY AGAINST AXIAL MOVEMENT INTO SAID PLUNGER AND PIVOTINGTHEREON TO EXERT A LATERALLY DIRECTED CONTACT PRESSURE UPON THE CONTACTOF SAID LAMP WHEN SAID LAMP IS SEATED IN SAID LAMPHOLDER.